Gale Warning 271, NWS Juneau, AK

Southeast Alaska Forecast Discussion
National Weather Service Juneau AK
528 AM AKST Sun Nov 27 2022

.SHORT TERM.../Through Sun night/ Building cold high pressure in
the Yukon is starting to have an effect on the area. Northerly
winds of 20 to 25 kt have started blowing down Lynn Canal and
parts of Stephens Passage overnight. However, There is not much
wind in other areas so far. Skies have also cleared out for many
areas of the panhandle. The exceptions are Yakutat, Skagway,
Haines, and parts of the southern panhandle where mid to high
level clouds linger. Temperatures have also fallen below freezing
for many areas overnight, but nothing colder then around 20 for
low elevation areas.

For the next 24 hours, the building high pressure in the Yukon is
the main driver of the forecast. Outflow winds will be gradually
increasing across the northern panhandle. Highest winds will be in
Lynn Canal where northerlies will be reaching near gale force by
late Sun night. Main forecast changes were a lowering of wind
speeds for today in some areas as the really cold air that is
associated with the Yukon high has not reached the area yet. This
mainly effects the wind speeds for Skagway, and downtown Juneau
and Douglas. The former for the cold air outflow (currently calm
winds at Skagway), and the latter for mountain wave formation
(wind shear is there and a weak inversion, but there is a lack of
cross barrier flow at the moment).

Looking at other forecast elements, dry and colder with some
areas of clouds are the main rule. Temperatures will be the main
concern as the main push of cold air starts to arrive tonight.
After seeing highs in the 30s today, temperatures will likely drop
into the 20s in the south, teens in the north, and single digits
in isolated areas tonight.

.LONG TERM.../ MONDAY THROUGH FRIDAY / Much colder and drier
pattern continues through at least Wednesday before we take note
of a developing low pressure system over the eastern Gulf by
Thursday. First off, coldest air this season poised to spill
southward out of the Yukon Monday through Wednesday. Previous
forecast had the temperature and wind forecasts well in tow and we
didn't make a lot of changes there. Big story is single digits
for overnight lows expected Monday night and again Tuesday night
across most of the northern and central Panhandle
communities...with daytime highs not getting out of the teens for
places like Haines, Skagway and the back valley areas around
Juneau.

The next thing to watch closely will be the strength of the
outflow winds Monday through Wednesday. This will have more
significant impacts to the marine community next week with higher
winds and increasing potential or freezing spray. For the land
areas, main concern is strong to very high wind potential Monday
night through Wednesday morning for Skagway, sections of Haines,
and downtown Juneau where the potential of 60-75 mph wind gusts
will be possible by Tuesday. For this reason, and the fact that
just about all of our guidance continues to converge for greater
confidence on higher winds for that timeframe, we have hoisted
the High Wind Watches for Skagway, Haines, and Juneau Boroughs.

The next thing of note in the extended range will be watching for
any potential of snow late Wednesday through Friday across the
area. ECMWF, GFS and Canadian models are fairly close in their
solutions of developing a strengthening surface low over the
northeastern Gulf as a shortwave dives south out of eastern Alaska
over the top of the central Alaska ridge, and progresses the low
to the south over the eastern Gulf through Friday. Given the
deeply cold and dry air attendant in place ahead of this system
dropping south out of the interior, we trended the forecast a bit
closer to the ensembles for the Thursday into Friday timeframe
but we didn't want to go as high as some of the deterministic
global models raising snow chances significantly that far out.

&&

.AVIATION...Northerly outflow has started across the SE panhandle,
clearing out most of the cloud cover, just a narrow band of mid to
high level clouds are moving east from the Yakutat area into the
northern coastal and northern panhandle. VFR flight conditions is
the forecast.

Surface winds expected to slowly increase Sunday and into
Sunday night favoring the typical outflow channels. Expect some
minor turbulence today near the terrain along outflow channeled
area and potentially some LLWS beginning to develop.

&&

.AJK WATCHES/WARNINGS/ADVISORIES...
PUBLIC...High Wind Watch from Monday evening through Wednesday morning
     for AKZ318-319-325.
MARINE...Small Craft Advisory for PKZ012-013-022-031>033-041>043-051>053.

&&

SHORT TERM...EAL
LONG TERM....JG
AVIATION...Bezenek

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